PPC/s390: [wasm-simd] Implement pmin/pmax

Port 3ba44311

Original Commit Message:

    F32x4 and F64x2 pmin and pmax were accepted into the proposal [0], this
    removes all the ifdefs and todo guarding the prototypes, and moves these
    instructions out of the post-mvp flag.

    [0] https://github.com/WebAssembly/simd/pull/122

R=zhin@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: I8b2ae60240f769e1f4c0b00e98d53846519b305e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2410806Reviewed-by: Junliang Yan <junyan@redhat.com>
Reviewed-by: Milad Farazmand <mfarazma@redhat.com>
Commit-Queue: Milad Farazmand <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/master@{#69893}

src/compiler/backend/ppc/instruction-selector-ppc.cc

@@ -2450,6 +2450,14 @@ void InstructionSelector::VisitF64x2Max(Node* node) { UNIMPLEMENTED(); }
 
 void InstructionSelector::VisitLoadTransform(Node* node) { UNIMPLEMENTED(); }
 
+void InstructionSelector::VisitF32x4Pmin(Node* node) { UNIMPLEMENTED(); }
+
+void InstructionSelector::VisitF32x4Pmax(Node* node) { UNIMPLEMENTED(); }
+
+void InstructionSelector::VisitF64x2Pmin(Node* node) { UNIMPLEMENTED(); }
+
+void InstructionSelector::VisitF64x2Pmax(Node* node) { UNIMPLEMENTED(); }
+
 // static
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {